CSC 161	Grinnell College	Spring, 2009

Imperative Problem Solving and Data Structures

Laboratory Exercise on Elementary C Programming

Goals

This laboratory exercise provides practice with basic elements of writing, editing, compiling, and running programs written in the C programming language.

Getting Started

Reading for this lab includes Walker, An Introduction to C Through Annotated Examples, Program 1 (quarts-1.c), pages 1-3. This link includes both commentary and a link to the directory of all of these C programs available on the World Wide Web. You will want to use this list of programs for this and subsequent labs.

Open a terminal window and move to your C subdirectory for this lab. Then use the emacs editor to create the quarts-1.c program discussed in the reading.
1. Start emacs with the command:
```
   emacs quarts-1.c &
```
2. Use the links for the reading to open the program quarts-1 in your browser. Then copy and paste it into the emacs window.
Compile and run the program in your terminal window by typing
```
   gcc -o quarts-1  quarts-1.c
   quarts-1
```
Run the program several more times by typing just quarts-1. (You need not compile the program each time — unless you have changed quarts-1.c.)
Make a few typographical errors in quarts-1.c, recompile, and observe what happens. In each case, check whether the program compiles, and whether the program runs. If the program does not compile, what happens if you try to run quarts-1?
Write a C program that reads values for pints, quarts, and gallons and determines the corresponding number of liters.

Although you can name this new program whatever you like, you should end the file name with .c for two reasons:
- You can identify the C programs quickly when you list files in your directory with the ls command.
- emacs recognizes the .c extension as indicating a C program, and emacs adjusts its setting to aid your editing for that type of file.
Refine your emacs environment as suggested in the reading for today's lab. That is, set the following options in the "Options" menu.
- Click the box for "Syntax Highlighting (Global Font Lock mode)"
- Click the box for "Paren Match Highlighting (Show Paren mode)"
- Click the box for "Case-Insensitive Search"
When done, click the "Save Options" choice in the "Options" menu.

Reminder: Since emacs is a very powerful editor, sometimes you will hit an erroneous key and then wonder what is happening. In such cases, the keystroke combination <ctrl>-g will stop any editing process within emacs!
Write a C program that reads a value for the radius of a circle and computes the circle's area and circumference.
Experiment with the emacs editor, following the lab on the Emacs Text Editor by Marge Coahran.

This document is available on the World Wide Web as

     http://www.walker.cs.grinnell.edu/courses/153.sp09/lab-intro-c.html

created 7 April 2008 last revised 25 January 2009
For more information, please contact Henry M. Walker at walker@cs.grinnell.edu.